Waterbeds have recently become a popular alternative to conventional beds because of their superior relaxation-inducing properties. Waterbeds have flexible bladders filled with water. A body supported by such a water-filled bladder displaces fluid in the bladder until an equilibrium condition is established to provide support of essentially uniform pressure on all portions of the body in contact with the bed.
Since the bladder is flexible, "bottoming out" can be a problem unless steps are taken to maintain the bladder top at a sufficiently high level above the bladder bottom. While this can be done by filling the bladder with an exceptionally large volume of water, the more reasonable and generally accepted approach has been to laterally support the bladder about its perimeter to hold the bladder top at the desired height.
A number of different types of lateral bladder supports have been used, and much of the development work in the field of waterbeds has been directed toward improvement of lateral bladder supporting apparatus. But significant problems regarding lateral support of water bladders have remained unsolved.
And it is clear that because of this the waterbeds of the prior art, including those on the market today, have major drawbacks which are recognized by the public. These drawbacks have limited the growth of the waterbed segment of the bedding market.
The lateral support most often used for a water bladder is a rigid wooden or plastic frame surrounding the upper flat surface of the deckboard which supports the water bladder on top of a pedestal. In these "sand-box" structures, the level of the bladder top surface is at or just below the upper edges of the rigid frame members.
Often, a watertight safety liner is placed between the bladder and the sand-box surfaces. Safety liners are required by law in many different states to retain the water in the event of leakage from the bladder and guard against the damage which could be caused to a building by major waterbed leakage. Such safety liners often also serve as insulating layers to help retain heat which has accumulated in the liquid.
While such sand-box structures support bladder perimeters and safety liners very well, they have some significant drawbacks. Getting in and out of such waterbeds and sitting on the sides are very uncomfortable exercises. For example, in getting out of the bed, the bladder naturally is depressed where one sits and it remains necessary to scale the wall which at that point is well above the level of the used portion of the bladder. In addition, having a bulky frame is somewhat contradictory to the advantage of collapsibility often ascribed to waterbeds.
Thus, efforts have been directed at eliminating the sand-box frame and at making waterbed mattresses more nearly like regular mattresses in the support they provide near their edges.
Such efforts have led to so-called "flotation systems," which are more than just a simple water bladders. Such flotation systems, while sometimes solving the aforementioned problems associated with sand-box type waterbed frames, themselves have distinct problems and disadvantages.
The common factor in all flotation systems appears to be the addition of substantial bulk around the perimeter of the water bladder to provide a water-free weight supporting surface along the bladder perimeter and to confine and support the bladder perimeter. Such additional bulk, which may be in a variety of forms, often comes as part of a mattress structure having a water bladder as its principal central element. Such bladders are often much smaller than standard waterbed bladders in order to make room for the additional bulk, and thus desirable flotation surface area is sacrificed.
One type of flotation system is an air-framed or perimeter chamber waterbed, in which an air-inflated annular member having one or more air compartments is secured, preferably by means of fluid-tight seals, to the perimeter of the water bladder. U.S. Pat. Nos. 3,778,852; 3,787,907; 3,918,110; 4,150,447; 4,491,993; and 4,501,036 are examples of such prior waterbeds.
Integrity problems arise in such systems because air is difficult to contain. And, because the air chambers are often formed with seals against the water bladder, strains are exerted on specific portions of the bladder and the risk of bladder rupture is increased. Furthermore, such air-framed waterbeds typically cannot be used without safety liners; but, since they provide no way to hold a safety liner in place, such waterbed mattresses are often used with a sand-box frame to support them along with a safety liner. This defeats part of their original purpose.
Another type of flotation system, sometimes referred to as a "composite" or "hybrid" waterbed mattress, has a number of cushions and rigidly interconnected internal frame members surrounding a water bladder with other cushions or pads covering the entire mattress. The outward appearance of such mattresses is very much like that of typical inner spring mattresses. U.S. Pat. Nos. 4,062,077; 4,186,455; 4,187,567; and 4,371,998 are representative of composite waterbeds.
The composite waterbed mattresses severely reduce the water flotation surface available to the user, and their covering layers reduce the flotation effect even in their central areas. Furthermore, composite waterbed mattresses are more complex in construction and much more expensive than typical waterbeds.
In yet another kind of flotation system, sleeves are attached to the edges of the water bladder to slidably receive self-contained chambers filled with air or foam. In some cases, substantially rigid members extend through the chambers and are rigidly connected at their ends to the ends of similar rigid members extending through the chambers in the adjacent sleeves. U.S. Pat. Nos. 4,181,990 and 4,334,331 are examples of this kind of system.
In these sorts of waterbeds, the seals joining the sleeves to the water bladder place a direct stress on the bladder, particularly when the sleeves are sat upon, which, of course, is intended. Such stress will tend to weaken the water bladder. And, as with the above-described air-framed waterbeds, there is no convenient way to use a watertight safety liner with this kind of waterbed. Furthermore, the appeaance of such waterbeds leaves much to be desired.
Each of the aforementioned waterbeds and water mattress perimeter support systems has significant drawbacks. There has been a need for an improved waterbed and waterbed perimeter support.